Virtual Environments

The problem: conflicting dependencies

Without a virtual environment, pip install puts packages in a single global location. Every project on your machine shares the same packages.

This causes conflicts. Project A needs requests==2.28. Project B needs requests==2.31. You can only have one version installed globally. Updating for Project B breaks Project A.

What a virtual environment does

A virtual environment is a self-contained directory that holds its own Python interpreter and its own set of packages. When you activate a virtual environment, pip install writes packages to that directory — not to the global location.

Each project gets its own environment. Project A has its packages. Project B has different packages. No conflicts.

Creating and activating

Python's built-in venv module creates virtual environments:

This creates a venv/ directory with a fresh Python installation. The directory name venv is a convention — you can name it anything, but most projects use venv or .venv.

Activate the environment to start using it:

Your terminal prompt changes to show (venv), confirming the environment is active. Now pip install writes to this environment only.

To deactivate and return to the global Python:

One rule to follow

Always create a virtual environment before installing packages for a project. This habit prevents dependency conflicts and keeps your global Python clean.